This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cancer cells rely more heavily on the de novo purine biosynthetic pathway than normal cells, which favor the salvage pathway as their main purine source. The main enzymatic targets in the de novo pathway for potential anti-cancer drug(s) are two folate-dependent transformylases, glycinamide ribonucleotide transformylase (GAR Tfase) and amino-imidazole carboxamide ribonucleotide transformylase (AICAR Tfase). The GAR Tfase structure was solved over a decade ago; however, the enzyme has many flexible loops in its active site that has compounded the problem of structure-based drug design and elucidation of its reaction mechanism. A recent fluorofolate complex structure has revealed that this complex seems to most closely represent the active state structure. A comprehensive comparative AutoDock study validated this new structural template for our continuing efforts on structure-based drug design. Our more recently determined AICAR Tfase structure presents a new target. In some ways it will be a better target because its kinetics are pH-independent and it has a relatively rigid active site. AICAR Tfase inhibitors also have potential use in treatment of inflammatory diseases, such as rheumatoid arthritis. On the other hand, it is highly desirable to discover alternative structural scaffold(s) to design a new generation of specific inhibitors, not just the traditional antifolates, We already used AutoDock to virtually screen the pharmacophore-representative NCI Diversity Set by utilizing NCRR/NBCR and Scripps sponsored computing clusters.